1. Field of the Invention
This invention relates to wells and well tools. More particularly it relates to apparatus for and methods of treating wells as by packing particulate material such as sand or gravel in the area of the production zone for purposes of sand control.
2. Description of the Prior Art
It is common sand-control practice in the oil and gas industry to install a screen in a well on a level with the producing formation and then pack particulates such as sand or gravel or the like around the screen, in the perforations and in any cracks and/or crevices connected therewith. These particulates are packed tightly and serve to brace or support the producing earth formation laterally to hold it in its natural place and thus keep formation sand and the like out of the well bore while allowing production fluids to enter the well bore and flow to the surface in the well-known manner.
It is also common to introduce the sand or the like particulate material into the well in the form of a slurry in which the individual grains are suspended in a gel, that is, in a gelatinous or viscous medium, to maintain these grains separated. This gelatinous substance coats each grain to lubricate it and enable it to flow more readily from the surface to the place of deposit downhole in the well and to protect it against fragmentation as a result of impacting with other grains during the trip. Ideally, after the sand is deposited around a well screen, it is "dehydrated" by applying a pressure thereto to squeeze the gelatinous substance out of it and cause the sand grains to move compactly into place to provide adequate support for the earth formation.
One of the problems encountered in such packing operations has been the inability to efficiently dehydrate the sand around and, in particular, above the screen. Thus, a substantial portion of the sand was necessarily left to settle by gravity, and for this much space was needed since 100 feet of gelatin coated sand may settle to less than 30 percent of that height.
In packing particulate material about a screen, the apparatus used includes a well packer with a screen attached to its lower end, a pipe string, and a service seal unit connected between the pipe string and the packer. The service seal unit is used in setting the packer and in directing the flow of fluids through the packer and screen to assure that the particulate material is deposited around the screen and that the excess particulate material is thereafter cleared from the well. Manipulation of the pipe string has been used to move at least a part of the service seal unit relative to the packer each time that it was necessary to change the flow pattern through the packing apparatus.
It is desirable to minimize manipulation of the pipe string in gravel pack type operations and thus reduce to a minimum the number of steps involved in the methods used. It is highly desirable to pack the sand or particulate material tightly about the well screen and in the perforations and other openings or cracks adjacent thereto so that the producing formation will be propped in place outside the casing and will remain there while production fluids freely flow from the formation through the casing perforations and into the well, then upward to the surface. It is desirable to minimize the distance between the screen and the packer and to minimize the time and costs of gravel-packing type operations.
Known prior art which relates to this present invention includes:
(a) U.S. Pat. No. 3,710,862; PA1 (b) U.S. Pat. No. 4,180,132; PA1 (c) U.S. patent application Ser. No. 06/493,147, now U.S. Pat. No. 4,519,451; and PA1 (d) Brochure No. OEC-5147 entitled "OTIS SINGLE-ZONE SAND-CONTROL SYSTEM" published by Otis Engineering Corporation, Dallas, Tex.
U.S. Pat. No. 3,710,862 issued Jan. 16, 1973 to Carter R. Young, et al, for METHOD AND APPARATUS FOR TREATING AND PREPARING WELLS FOR PRODUCTION. This patent discloses apparatus and methods for gravel packing a well.
U.S. Pat. No. 4,180,132 issued to Carter R. Young on Dec. 25, 1979 for SERVICE SEAL UNIT FOR WELL PACKER. This patent discloses a service seal unit for use in gravel packing apparatus and methods similar to those disclosed in U.S. Pat. No. 3,710,862, but it includes means actuable by hydraulic pressure for setting the packer and means associated therewith for preventing premature setting of the packer.
Patent application Ser. No. 06/493,147 was filed May 9, 1983 by Floyd R. Gray and Dennis D. Rood for WELL TREATING EQUIPMENT AND METHODS. This patent application discloses well gravel packing apparatus and methods which are improvements over the apparatus and methods taught in U.S. Pat. Nos. 3,710,862 and 4,180,132, just mentioned.
Brochure OEC-5147 entitled "OTIS SINGLE-ZONE SAND-CONTROL SYSTEM, published by Otis Engineering Corporation, Dallas, Tex., discloses well gravel packing apparatus and methods similar to those provided by the present invention.
None of the prior art of which applicant is aware shows or teaches methods of or apparatus for gravel packing wells and utilizing a normally closed lateral opening in the service seal unit which will open automatically when the sand or the like becomes packed or dehydrated around the screen to short-circuit the fluid flow path to permit further circulation of sand-laden fluids, packing, and dehydration without having to rely on gravitational settling of the sand or the like in the annulus, which requires excessive, expensive longitudinal space between the packer and the screen.
The prior art patents, U.S. Pat. Nos. 3,710,862 and 4,180,132 and U.S. patent application, Ser. No. 06/493,147, all mentioned hereinabove, are incorporated herein for all purposes by reference thereto.